A typical loading dock of a building includes an exterior doorway with an elevated platform for loading and unloading vehicles, such as trucks and trailers. To compensate for height differences between the loading dock platform and an adjacent bed of a truck or trailer, many loading docks have a dock leveler. A typical dock leveler includes a deck or ramp that is pivotally hinged along its back edge to vary the height of its front edge. A retractable extension plate or lip pivots or translates outward from the deck's front edge to span a gap between a rear of the truck bed and the front edge of the deck. The deck and lip provide a bridge between the dock's platform and the vehicle's bed so that personnel and material handling equipment can readily move on and off the vehicle during loading and unloading operations.
To help shield against weather while a vehicle is being serviced at the dock, a seal is usually installed around the perimeter of the doorway. Such seals are typically installed along upper and side edges of the doorway to help seal any air gaps that may otherwise exist between a face of the building and the rear of the vehicle. The dock leveler lip, when resting upon the rear of the vehicle, may provide a seal to a portion of a lower end of the doorway.
The area or pit underneath a dock leveler's deck, however, is usually exposed to outside air. This can create problems, particularly when there is a significant temperature differential between the indoor and outdoor air. Warm outside air, for example, may condense underneath a relatively cool deck of a dock leveler used in a cold storage warehouse. The condensation can promote corrosion of various parts of the dock leveler. Conversely, a heated building during the winter may lose a significant amount of heat by thermal conduction through the deck, as cold outside air cools the deck from underneath. Moreover, when the indoor air is relatively warm while the deck is cooled by outside air, condensation can form on top of the deck.